The present invention relates to the treatment of a patient by use of laser energy. More specifically, the present invention relates to treatment of a large volume, such as a large tumor, by use of minimal incisions.
In interstitial laser hyperthermia, a tumor volume is heated to its biological critical temperature to create permanent damage to the tissue so that a lesion is formed in place of the volume. For neurological applications, a burr hole drill is made at the incision point on the skull to allow access of the laser fiber through a guiding tube to the volume of interest. Using a YAG laser, a typically treated volume created under typical laser power controlled by the heat propagation in live tissue is on the order of an ellipsoid with axes of (10, 5, 5) in millimeters. In other words, and assuming the major axis extended in the x direction, the ellipsoid would extend 10 millimeters in the x direction and would have minor axes of 5 millimeters in both the y and z directions. However, in most cases, the tumor volume is larger than the ellipsoid created by a single laser fiber. As shown in the prior art simplified schematic of FIG. 1, an optical fiber 10 extends into the head 12 of a patient by way of a burr hole 14. More specifically, the fiber 10 extends through a guiding tube 16 such that the tip of the fiber 10 is within or immediately adjacent to a tumor volume 18. Laser energy is then supplied through the optical fiber 10 to create an ellipsoid heat/lesion volume 20 of the size previously discussed. As illustrated schematically in FIG. 1, the heat/lesion volume 20 is smaller than the tumor volume 18. Accordingly, lesions would have to be made at different locations in order to cover the tumor volume 18.
In order to create a lesion larger than the typical ellipsoid, multiple laser fibers spaced apart in parallel trajectories have been used to create a heat front that encloses the tumor volume. Alternately, laser energy is applied by multiple fibers spaced apart through different trajectories when access is limited by critical anatomical features such as a blood vessel. Whether one is using spaced apart parallel trajectories or using different nonparallel trajectories, multiple burr holes are often required to allow multiple guiding tubes to access the tumor. (This is true whether the laser energy is applied simultaneously through different fibers or the laser energy is applied in sequence, using one optical fiber at a time.) The requirement for multiple burr holes increases the invasiveness of the operation and makes surgical planning more complicated because multiple trajectories require access through a larger region of anatomy.